Comparison of Feeding Functional Morphology Development in North American Esocids

Esocidae is a family of freshwater fishes within order Esociformes known for its long, cylindrical bodies, duck-bill snouts, and an impressive number of sharp teeth. There are four species, including two subspecies, in North America with areas of overlap of their geographic distribution. These ambush predators change diets from invertebrate prey to vertebrate prey during their first year of life, and the timing of this shift varies between species. In particular, the sister species Esox lucius (Northern Pike) and Esox masquinongy (Muskellunge) overlap in the upper Midwest, but E. masquinongy transitions to a vertebrate diet sooner in its development than E. lucius. This thesis focused on developmental changes of the lower jaw functional morphology and cranial geometric morphometrics and comparing those changes between two species: Esox lucius and Esox masquinongy. While both species follow a similar trajectory across development, E. masquinongy displayed traits consistent with faster lower jaw movement and a more streamlined cranium, both attributes helpful for ambush predators to effectively capture fast moving prey